Protective device



Dec. 25, 1928.

1,696,611 G. MCDONALD PROTECTIVE DEVICE Original Filed May 28, 1925 2 $heats-Sheet 1 Inventor": Gordon RMC DonaLd,

' V i s Attorneu.

Dec. 25, 1928. 1,696,611

a. R. MCDONALD PROTECTIVE DEVICE Original Filed May 28, 1925 2 sheets sheet 2 EM/ZQ rill/11111171712111!!!III/I11;

Inventor": Gordon RMc Donald,

b fl 1g Hi$ Attorney.

PATENT OFFICE.

GORDON B. IODONALD, OF BCHIHECTADY,

zmw YORK, ABBIGITOB '10 mo- TBIG comm, A CORPORATION 01' mrw You no'rncnvn amen Application fled Kay 28, 1925, Serial No. 33,584. Renewed September I, 1988.

My invention relates tov improvements in protective devices and has for an object to provide an improved protective device which operates in response to the rate of increase of current at some predetermined value of current when the currentincreases slowly and at a lower value of current when the current increases rapidly.

My invention will be better understood from the following description takenin connection with the accompanying drawings, and its scope will be pointed out in the appended clalms.

In the accompanying drawings, Fig. 1 illustrates an embodiment of my invention in a circuit breaker, and Figs. 2 and 3 illustrate the embodiment of my invention shown in Fig. 1 in elevation and perspective respectively, certain parts being shown cut away in Fig. 3.

Fig. 1 shows a circuit breaker mounted on a switchboard 1 and comprising a movable circuit controlling element such as a brush 2, which is arranged to bridge terminal studs 3 and 4. The circuit breaker also comprises secondary contacts 5 and 6 which may be suitably disposed in an arc chute 7 provided with a blowout coil 8. The brush 2 is mounted on an arm 9 pivoted at 10 and is arranged to be moved to the circuit closed position by a solenoid comprising a plunger 11 and to be held in the circuit closed position by a restrained underset toggle comprising links 12 and 13. The toggle is restrained by a latching mechanism comprising a main latch 14 arranged to engage the link 13 at 15 and an auxiliary latch'16 arran ed to engage the main latch 14 at 17, the Iatches being biased to latching position by a slpring 18.

In ig. 1, the circuit breaker is shown in the circuit closed position, the brush 2 being held against the bias of gravity and the brush pressure by the toggle and latching mechanism, To trip the circuit breaker, that is, to release the brush 2 for movement to the circuit open position, the auxiliary latch 16 is moved counterclockwise about its pivot 10. This releases the main latch 14, which then slips oil the link 13 and permits the toggles 12, 13 to buckle. The arm 9 is then free to turn clockwise.

For tripping the circuit breaker, that is, releasing the latch 16 in response to abnormal circuit conditions, I provide means, in-

dicated generally as 19, which is o rative in response to the rate of increase 0 a con- .tinuous current at some predetermined value of current when the current increases slowly and at a lower value of current when the current increases rapidl shown more in detail in F prises an energizing windin which in'the case of adirect current circult breaker may be the terminal stud 4 as shown, an armature 20 having a portion 21 which is arranged on movement 0 counter-clockwise as seen in Fig. 2 to en ge the latch 16 whereby to release the latching .mechanism, and a magnetizable member 22 comprising two branches or main and shunt or parallel flux paths 23 and 24 for the flux through the armature. These aths present spaced poles 25, 26 of like po arit on opposite sides of the armature. e magthe armature in one direction,

This means, igs. 2 and 3, comnetizable member 22 may be U-shaped to' straddle the stud 4 and may be supported by being secured thereto by a suitable fastening means such as a screw 27. The shunt flux path comprises the magnetizable elements 24, 26, 28 and 29. The pole piece or member 26 may be adjustably positioned in the member 29' so as to provide for changing the gap between the armature 20 and the pole 25.

Normally the distribution of the flux of the magnetizable member 22 in the main and shunt flux paths is such that the armature 20, is maintained against the pole 26 of the shunt flux ath, the restraining eifect being increased Iry the bias of gravity and suitable adjusting means such as a spring 30, the tension of which is arranged to be varied by a screw 31 mounted in a suitable supporting member 32. In order that the armature 20 may be attracted to the pole 25 on the occurrence of a slowly increasin continuous current in the winding or stud 4-, the shunt flux path 24 is arranged to saturate at some predetermined current such that the pull between the armature 20 and the pole 25 exceeds the pull between the armature 20 and the pole 26, the bias of gravity and the tension of the spring 30. When this occurs, the portion 21 of the armature 20 moves downward and turns the latch 16 counterclockwise to trip the circuit breaker. Thus in the case of overloads, that is, slowly increasing current, the attractive effort of the shunt flux path increases up to a certain point, that is, the current necessary 110 to saturate the shunt flux path. This attractive efi'ort' then becomes substantially constarrtaand further increase in the current increases the .pull between the armature 20 and the pole until the armature,-

s 25 and' 26, is moved I and shunt vpaths, that the armature 20 will be attracted. to the pole 25 at a lower value of current than is the case when the'current increases slowly. In this case, since the current is rapidly increasing, the shunt flux path does not. saturate because the closed circuit winding 33 delays or chokes back the flux in the member 24 so that substantially all the flux is turned back or diverted into the main flux path 23 and the restraint or pull of the shunt flux path is substantially nullified.

While I have shown and described only one embodiment of my invention, I do not desire to be limited to the exact arrangement shown but seek to cover in the appended claims all those modifications that fall within the spirit and scope of my invention.

oi the spring 30; and

2. In combination with a circuit breaker and a latching mechanism for holding the circuit breaker closed, means for releasing the latching mechanism on the occurrence of abnormal circuit conditions comprising, a magnetizable member having main and shunt flux paths presenting two spaced poles,

such as to maintain said end of the armature against the pole of the shunt flux path characterized by the fact that the shunt path is arranged to saturate on a predetermined value of continuous current in said wind ng. 7 to effect the movement of the armature to the pole of the main path when a continuous current ncreases slowly in said winding to 'a value exceeding said predetermined value whereby to release the latching mechanism and by the fact that the shunt path is provided witha closed circuit winding to cited; a change in the distribution of the flux of said member in said paths on a rapidly increasing continuous current whereby to effeet the movement of the armature to the pole of the main path on a rapidly increasing current before the current reaches said predetermined value to release the latching mechanism.

3. In a circuit interrupting device wherein a movable circuit controlling element is provided with a latching mechanism for holding theelement in circuit closing position, means for efl'ectin'g the release of the latching mechanism on the occurrence of abnormal circu t condltlons comprising an and a latching mechanism for holding the, energizing winding, a magnetizable member circuit breaker closed, means for releasing the latching mechanism on the occurrence of abnormal circuit conditions comprising, an armature having a'portion arranged on movement of the armature in one direction to engage the latching mechanism whereby to release the same, an energizing winding, a magnetizable member comprising two branches arranged to form parallel magnetic paths for the flux through the armature, one

of said branches being arranged magnetically to saturate on the occurrence of a slowly increasing continuous current in said winding whereby to efl'ect movement of the armature in said direction when the currenthas reached a predetermined value, and means for efi'ecting movement of the armature in said direction on the occurrence of a rapidly:

increasing continuous currentin said wind- 1ng before the current reaches said predetermined value comprising a closed circuit winding on the branch arranged to saturate for controlling the distribution of the flux of said member in the branches thereof.

having two branches arranged to present spaced poles of like polarity, one of said branches having a limited flux capacity so as to saturate on a slowly rising continuous current in said winding when the current reaches a predetermined value, an armature having one end movable between said poles, said armature being arranged normally to be held against the pole of the branch of limited flux capacity and to be attracted to the other pole when a slowly rising continuous current in said winding exceeds said predetermined value whereby to efi'ect the release of said latching mechanism, and means for causing the armature to be attracted to said other pole on the occurrence of a rapidly increasing continuous current in saidwinding before the current reaches said" predetermined. value whereby to effect the release of" said Iatchingmeeh'anismtcnm; prising a closed circuit winding on. the branch oflimited flux capacity for controlling the distribution of the flux of said member in the branches thereof.

In a direct current circuit breaker magnetizable member having two branches.

arranged to resent spaced oles of like polarity, one 0 said branches iaving a limited flux capacity so as to saturate on a slowly rising current when the current reaches a predetermined value, a pivoted armature aving one end movable between said poles, said end of the armature being arranged normally to be held against the pole of the branch of limited flux capacity and to be attracted to the other pole on the occurrence of a slowly rising current exceeding said predetermined value wherebv to effect the release of said latching mec anism and means for causing the armature to be attracted to said other pole on the occurrence of a rapidly risin current before the current reaches said pre etermined value whereby to effect the release of said latching mechanism comprising a closed circuit winding on the branch of limited flux capacity for controlling the distribution of the flux of said member in the branches thereof.

5. In a device of the class described, a magnetizable member having main and shunt flux paths presenting two spaced poles, an energizing winding for said member, an armature having one end movable between said poles, means for biasing said end of the armature to the pole of the shunt path said member being constructed so that the distribution of the flux in said paths with a continuous current in said winding below a predetermined value is such as to assist the biasing means to hold the end of the armature against the pole of the shunt path, said shunt path being arranged to saturate with a continuous current in said winding above said predetermined value to effect the movement of the end of the armature to the pole of the main path when a continuous current increases slowly in said winding, and a closed circuit winding associated with said shunt path for effecting a chan e in the distribution of the fluxes in sai paths on a rapidly increasing continuous current in said windin whereby to effect the movement of the an of the armature from the pole of the shunt flux path to the pole of the main flux path at a lower value of the current than when the current is increasing slowly.

In witness whereof, I have hereunto set my hand this 26th day of May, 1925.

GORDON R. MoDONALD. 

